Improved Lithium-Ion Transport Within the LiNi 0.8 Co 0.15 Al 0.05 O 2 Secondary Cathode Particles Through a Template-Assisted Synthesis Route

Herein, we report a sacrificial carbon fiber (CF) template-assisted synthesis of LiNi0.8Co0.15Al0.05O2 (C-NCA) by the Pechini method. An anisotropic primary particle morphology with an interconnected microstructure is obtained, originating from local overheating and oxygen-deficient zones induced by combustion of the CFs during high-temperature lithiation. Moreover, the particles assembled around the CFs demonstrated denser packing compared to the reference bare NCA (B-NCA) synthetized in the absence of the CF template. The anisotropic surfaces facilitate ion transport and stabilize the structure for high voltage and temperature operation. C-NCA||Li metal cells exhibit a reversible capacity of 106 mA h g–1 at 10 C and are able to retain 96% of their initial capacity as the C-rate is reverted to 0.1 C. The state of health of C-NCA||graphite full cells remains at 70% after 200 cycles at 0.33 C within 2.8–4.3 V. The results outperform the B-NCA cell, exhibiting a significant loss over 66 cycles while delivering only 50% of its initial capacity. The synthesis method allows for a straightforward route for tailoring the particle size, shape, and crystallinity, enabling the development of stable nickel-rich cathode materials, even at an upper cutoff voltage of 4.5 V or an operating temperature of 60 °C

Practical Implementation of Magnetite-Based Conversion-Type Negative Electrodes via Electrochemical Prelithiation

We report the performance of a conversion-type magnetite-decorated partially reduced graphene oxide (Fe3O4@PrGO) negative electrode material in full-cell configuration with LiNi0.8Co0.15Al0.05O2 (NCA) positive electrodes. To enable practical implementation of the conversion-type negative electrodes in full cells, the beneficial impact of electrochemical prelithiation on mitigating active lithium losses and improving cycle life is shown here for the first time in the literature. The initial Coulombic efficiency (ICE) of the full cells is improved from 70.8 to 91.2% by prelithiation of the negative electrode to 35% of its specific delithiation capacity. The prelithiation is shown to improve the surface passivation of the Fe3O4@PrGO electrodes, leading to less electrolyte reduction on their surface which is prominent from the significantly lowered accumulated Coulombic inefficiency values, lower polarization growth, and doubled capacity retention by the 100th cycle. The reduced surface reactions of the negative electrode by prelithiation also aids in reducing the extent of aging of the NCA positive electrode. Overall, the prelithiation leads to a longer cycle life, where a retained capacity of 60.4% was achieved for the prelithiated cells by the end of long-term cycling, which is 3 times higher than the capacity retention of the non-prelithiated cells. Results reported herein indicate for the first time that the electrochemical prelithiation of the Fe3O4@PrGO electrode is a promising approach for making conversion negative electrode materials more applicable in lithium-ion batteries